MUSHROOM PESTS AND HOW TO CONTROL THEM. 7 



No direct observations on the life history of this species have been 

 made, but judging from that of rehited species it is al)out as follows: 

 The eggs, which are large in proportion to the size of the mites, are 

 laid in or about the mycelium or on the young developing caps. 

 They hatch in a short time into the characteristic 6-legged young, 

 which soon become mature. The time from the deposition of the 

 egg to the maturity of the mite has not, so far as the writer knows, 

 been worked out accurately, but it undoubtedly occupies only a few 

 days. It is on this account that the mite is able to increase so rapidly, 

 apparently as if by magic, and thus give rise to the theory of spon- 

 taneous generation sometimes advanced to explain this condition. 



Under certain conditions the hypopus or migratory stage is pro- 

 duced. This stage, so far as know^n, is peculiar to the family Tyro- 

 glyphidae, to which this mite belongs, and is very remarkable. The 

 mite develops a hard, chitinous covering, has no mouth parts, and is 

 i)rovided with short legs insufficient for walking. On the ventral 

 surface of the body is an area provided with sucking disks, by means 

 of which the hypopus attaches itself to an insect and is so transported 

 to suitable breeding grounds in other localities. On arrival at a 

 suitable breeding place the mite detaches itself from its insect host, 

 molts, and soon becomes adult. During the hypopus stage the mite 

 takes no food and causes no injury to the insect which carries it. 

 This peculiar stage is the natural means for the distribution of tliQ^ 

 mite to new localities, and is in many cases responsible for its appear- 

 ance in localities far from previously infested beds. 



In addition to the means mentioned above, the mite may obtain 

 access to mushroom houses in infested compost or in spawn from 

 infested houses. The greater part of the infestation, however, prob- 

 ably takes place through the agency of the small flies which frequent 

 mushroom houses and which carry the hypopus stage of the mite 

 from one house to another. 



REMEDIES. 



Little can be recommended for the control of the mushroom mite 

 after it has once become established in a house. Owing to the absence 

 of breathing pores it is practically unaffected by fumigants suitable 

 for the control of other mushroom pests, while applications of sul- 

 phur, tobacco dust, and other insecticides to the beds seem only to 

 prove slightly inconvenient to the mite. It is one of the most stub- 

 born pests encountered in mushroom culture, and may be brought 

 into the house in almost any manure that is used for the bed. When 

 in the hypopus stage it is capable of prolonged suspension of vitality 

 and is likeh" to remain in the house for an almost unlimited time 

 without death. The only measures, therefore, that may be considered 

 are those of prevention. 



